I was unfortunate! I received a Pokemon with Pokerus from my BW GTS, thought it was my lucky day! (Note: prior to this, I did not know about Pokecheck yet.) So I happily spread that contagius decease!
Then one day I learnt about Check, so I decided to try using it. It said the Pokerus it was ineffected with was from hack. So I have to released those hard trained Pokemon.... Devastating...